Generally, the common input device of a computer system includes for example a mouse, a keyboard device or a trackball. Via the keyboard device, the user may input characters and instructions into the computer system. As a consequence, most users and most manufacturers pay much attention to the development of keyboard devices.
Hereinafter, the configurations and functions of a conventional keyboard device will be illustrated with reference to FIG. 1. FIG. 1 is a schematic view illustrating the outward appearance of a conventional keyboard device. The surface of the conventional keyboard device 1 includes plural keys. These keys include ordinary keys 10, numeric keys 11 and function keys 12. When one or more keys are depressed by the user, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the depressed key or keys. For example, when the ordinary keys 10 are depressed, corresponding English letters or symbols are inputted into the computer system. In addition, the function keys 12 (F1˜F12) can be programmed to cause corresponding application programs to provide certain functions.
With the maturity of computing technologies, the conventional keyboard 1 that has basic functions fails to meet the users' requirements. For this reason, the keyboard manufacturers make efforts in designing novel keyboards with diversified functions. Recently, an illuminated keyboard with a luminous function has been disclosed. FIG. 2 is a schematic side view illustrating a conventional illuminated keyboard. As shown in FIG. 2, the illuminated keyboard 2 comprises a key 20, a metallic base plate 21, a membrane switch circuit module 22, a light source 23 and a light guide plate 24. The key 20 comprises a keycap 201, a scissors-type connecting member 202 and an elastic element 203. From top to bottom, the keycap 201, the scissors-type connecting member 202, the elastic element 203, the membrane switch circuit module 22, the metallic base plate 21 and the light guide plate 24 of the illuminated keyboard 2 are sequentially shown. The light source 23 is arranged beside the light guide plate 24. Via a flexible printed circuit (FPC), the light source 23 is connected with a circuit board (not shown) of the illuminated keyboard 2. In addition, electricity is transmitted to the light source 23 through the flexible printed circuit 25. The light source 23 is used for emitting a light beam B. An example of the light source 23 is a light emitting diode (LED). In addition, the elastic element 203 is a transparent rubbery element.
In FIG. 2, the light guide plate 24 is used to guide the light beam B, and thus the light beam B can be diffused to the whole keyboard. In addition, the light guide plate 24 is used to change the propagating direction of the light beam B, so that the light beam B is moved upwardly. The membrane switch circuit module 22 is disposed on the metallic base plate 21. Moreover, the metallic base plate 21 has a first fixing structure 211, a second fixing structure 212 and two partition plate openings 213. Via the partition plate openings 213, the light beam B will be incident into the membrane switch circuit module 22. The keycap 201 comprises a first keycap fixing structure 2011, a second keycap fixing structure 2012 and a light-transmissible region 2013. The scissors-type connecting member 202 comprises a first frame 2021 and a second frame 2022. A first end 2021A of the first frame 2021 is connected with the second fixing structure 212. A second end 2021B of the first frame 2021 is connected with the first keycap fixing structure 2011. A first end 2022A of the second frame 2022 is connected with the first fixing structure 211. A second end 2022B of the second frame 2022 is connected with the second keycap fixing structure 2012.
Please refer to FIG. 2 again. When the key 20 is depressed and moved downwardly with respect to the metallic base plate 21, the first frame 2021 and the second frame 2022 of the scissors-type connecting member 202 are switched from an open-scissors state to a stacked state. In addition, as the keycap 201 is moved downwardly to press the elastic element 203, the elastic element 203 is sustained against the membrane switch circuit module 22, and thus a key signal corresponding to the depressed key 20 is generated. Whereas, when the depressing force exerted on the key 20 is eliminated, an elastic force provided by the elastic element 203 is acted on the keycap 201. Due to the elastic force, the keycap 201 is moved upwardly with respect to the metallic base plate 21, and the first frame 2021 and the second frame 2022 of the scissors-type connecting member 202 are switched from the stacked state to the open-scissors state. Consequently, the keycap 201 is returned to its original position. After the light beam B is emitted by the light source 23, the light beam B is directed to the light guide plate 24. By the light guide plate 24, the propagating direction of the light beam B is changed. Consequently, a portion of the light beam B is sheltered by the metallic base plate 21, but the other portion of the light beam B is guided toward the membrane switch circuit module 22 through the partition plate openings 213. Then, the light beam B successively passes through the membrane switch circuit module 22, the elastic element 203 and the light-transmissible region 2013 of the keycap 201, thereby illuminating the key 20.
The conventional illuminated keyboard, however, still has some drawbacks. For example, since the majority of the light beam B emitted by the light source 23, which is disposed under the metallic base plate 21, is sheltered by the metallic base plate 21, the conventional illuminated keyboard fails to be uniformly illuminated.